1. Field of the Invention
The present invention relates to what is called a front-opening interface mechanical standard (FIMS) system that is used to transfer wafers stored in an interior of a transfer container called a pod between semiconductor processing apparatuses in a semiconductor manufacturing process, etc. More specifically, the present invention relates to a pod called a front-opening unified pod (FOUP) or a closed container for storing wafers and a method of fixedly attaching a lid to such a pod from which the lid has been detached to close an opening of the pod in an FIMS system for opening/closing the lid of the pod to allow transfer of wafers into/out of the pod. The present invention also relates to a lid opening/closing system that preferably carries out the method.
2. Description of the Related Art
Conventionally, the semiconductor manufacturing
Conventionally, the semiconductor manufacturing process had been performed in what is called a clean room that is constructed by establishing a high degree of cleanliness in the room in which semiconductor wafers are handled. In recent years, however, in view of an increase in the wafer size and with a view to reduce cost incurred in maintenance of the clean room, there has been adopted a method of keeping highly clean only an interior of a processing apparatus, a pod (container for storing wafers), and a mini-environment through which substrates are transferred between the pod and the processing apparatus.
The pod includes a substantially cubical main body (closed container) which has shelves provided therein so as to be capable of holding a plurality of wafers in a parallel and separated state and an opening provided on one of the sides or external walls thereof through which wafers can be transferred into/out of the pod, and a lid for closing the opening. The pods as described above which have an opening provided not on the bottom but on one lateral side thereof (i.e. side to be just opposed to the mini-environment) are collectively called front-opening unified pods (FOUPs). The present invention mainly pertains to technologies that use the FOUP.
A structure that defines the above-mentioned mini-environment includes a first opening portion to be opposed to the opening of the pod, a door that closes the first opening portion, another processing apparatus side opening portion provided on the semiconductor processing apparatus side, and a transferring robot that is adapted to enter the interior of the pod through the first opening portion to hold a wafer and transfer the wafer into the processing apparatus through the another processing apparatus side opening portion. The structure that defines the mini-environment further has a support table for supporting the pod such that the opening portion of the pod is placed just in front of the door.
On the top surface of the support table, there are provided positioning pins to be fitted into positioning holes provided on the bottom surface of the pod to regulate the placement position of the pod and a clamp unit for engaging a clamped portion provided on the bottom surface of the pod to fix the pod onto the support table. Typically, the support table is adapted to be movable toward and away from the door over a predetermined distance. When wafers in the pod are to be transferred into the processing apparatus, the pod placed on the support table is moved until the lid of the pod comes into contact with the door, and then after contact, the lid is detached from the opening portion of the pod by the door (see Japanese Patent Application Laid-Open No. 11-288991). By those operations, the interior of the pod and the interior of the processing apparatus are bought into communication with each other through the mini-environment. After that, wafer transferring operations are allowed to be performed repeatedly. All of the support table, the door, the first opening portion, a mechanism for opening/closing the door, a wall partially defining the mini-environment and having the first opening portion, and other components collectively constitute what is called a front-opening interface mechanical standard (FIMS) system.
As disclosed in detail in Japanese Patent Application Laid-Open No. 2001-077177, a lid of a conventional pod is provided with an engagement tongue that is extendable/retractable outwardly beyond/into the outer periphery of the lid, and a receiving hole with which the engagement tongue engages is provided at a position in the pod corresponding the engagement tongue. The engagement tongue and the receiving hole function as an engagement means for fixedly attaching the lid to the pod. In a conventional structure, the pod and the lid are brought into an engagement state and a disengaged state by extension and retraction of the tongue. When, for example, the opening of the pod is closed by the lid, the tongue provided on the lid may sometimes fail to be inserted precisely into the receiving hole on the pod due to the presence of a foreign matter(s) between the opening and the lid or a positional displacement resulting from accumulation of errors such as a positional error of the pod on the support table and an operation error of the door etc. In such cases, if it is mistakenly determined that the opening of the pod is completely closed by the lid, subsequent operations such as transportation of the pod are performed, and there is a fear in that the lid is dislocated or detached from the pod, for example, during transportation of the pod. A countermeasure to the above-mentioned situation that has been under development currently is to arrange a sensor that detects the state of the tongue to detect displacement of the tongue from a normal position, thereby reliably determining whether or not the opening is closed successfully, as disclosed in Japanese Patent Application Laid-Open No. 2001-077177.
In pods having a conventional size, there is not much risk of occurrence of a failure in closing by the lid by virtue of the relationship among the sizes of the lid, the receiving hole on the pod, and the projecting portion of the tongue. In addition, the operation of the tongue can be detected relatively easily, and it is possible to determine whether the closing is successful or not by detecting abnormality in a mechanism that operates the tongue. However, an increase in the size of the pod with an increase in the wafer diameter in recent years necessitates a decrease in the size of the engagement portion of the tongue relative to the size of the pod, relatively. For this reason, the risk of occurrence of a failure in closing may increase, or there may be cases where an operation error of the tongue cannot be detected even when a failure in closing occurs. In addition, pods that are currently used are not provided with such a mechanism for detecting the tongue. When an attempt is made to actually provide this method, it is necessary to replace or modify all the pods. Further, it may be sometimes difficult to provide the above-mentioned mechanism depending on a shape, etc. of the pod.